Phong Nha – Ke Bang National Park is called the kingdom of grottoes. Since 1920, this area has been known as a famous cave system. Then the Phong Nha cave was organized for visiting by French since 1937. Nowadays the cave system here has been discovered and measured in detail by the British Royal Cave Association, the Science University of Ha Noi National University. They found and recorded the outstanding values of the cave system in Phong Nha – Ke Bang.

Phong Nha - Ke Bang grottoes are the oldest age in South-East Asia that the establishment concern to tectonics faults in third period (35 million years) at the same time with separation and stretching takes shape Chinese sea. The cave system is developed above the largest limestone area in South-east Asia with very ancient age from the late Devon period (377 million years) to the Permian period (250 million years).

The Phong Nha - Ke Bang Caves consist of the Phong Nha Cave system, with 9 caves of various sizes and the Vom Cave system, with 8 caves of various sizes. The total length of the Phong Nha - Ke Bang Caves is 86,839m (from 2005). In these caves, there are many underground rivers. In some places they appear on the ground and all the inlets of underground rivers flow down to the Chay and Son Rivers. Finally, they combine with the Gianh River and run to the sea.

At the present Phong Nha and Tien Son cave always open to welcome to visitors to discover marvelous beauty and hidden values here.